[PATCH] D30375: Function with unparsed body is a definition

[Serge Pavlov via Phabricator via cfe-commits]

sepavloff created this revision.

While a function body is being parsed, the function declaration is not considered
as a definition because it does not have a body yet. In some cases it leads to
incorrect interpretation, the case is presented in
https://bugs.llvm.org/show_bug.cgi?id=14785:

      template<typename T> struct Somewhat {
        void internal() const {}
        friend void operator+(int const &, Somewhat<T> const &) {}
      };
  void operator+(int const &, Somewhat<char> const &x) { x.internal(); }

When statement `x.internal()` in the body of global `operator+` is parsed, the type
of `x` must be completed, so the instantiation of `Somewhat<char>` is started. It
instantiates the declaration of `operator+` defined inline, and makes a check for
redefinition. The check does not detect another definition because the declaration
of `operator+` is still not defining as does not have a body yet.

This change solves this problem by using flag `WillHaveBody`. It introduces new
semantic action `ActOnStartFunctionBody`, which set this flag so that definitions
that do not have body (such as deleted functions) do not have this flag.

This change fixes PR14785.

The fix requires https://reviews.llvm.org/D26065 be applied otherwise diagnostics is awful.


https://reviews.llvm.org/D30375

Files:
  include/clang/AST/Decl.h
  include/clang/Sema/Sema.h
  lib/AST/Decl.cpp
  lib/Parse/Parser.cpp
  lib/Sema/SemaCUDA.cpp
  lib/Sema/SemaDecl.cpp
  lib/Sema/SemaTemplateInstantiateDecl.cpp
  test/SemaCXX/friend2.cpp

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